Effect of a nonmagnetic impurity on the superconducting transition temperature in layered structures with a non-phonon-mediated pairing mechanism

Abstract

The effect of nonmagnetic impurities on the superconducting transition temperature Tc in superconductors with a non-phonon-mediated (nonphononic) mechanism of superconductivity is investigated. Two features inherent to high-Tc superconductors are taken into account: the overlap of the energy bands, and the variable density of charge carriers. The cases of s and dx2−y2 symmetry of the order parameter are considered. It is demonstrated that the Anderson theorem is violated in the case of s symmetry of the order parameters, both on account of interband scattering of electrons on impurities and on account of intraband scattering due to the electron–hole asymmetry in systems with a nonphononic mechanism of superconductivity. Analytical expressions are obtained for the value of Tc in the regions of small and large impurity concentrations, and numerical solutions of a self-consistent system of equations are found. The influences on Tc due to various mechanisms (the change in the chemical potential and in the int...